1. Field of the Invention
The present invention relates generally to wireless communication networks, and more particularly to a system and method for transmission parameter control for an antenna apparatus with selectable elements.
2. Description of Related Art
In communications systems, there is an ever-increasing demand for higher data throughput and a corresponding drive to reduce interference that can disrupt data communications. For example, in an IEEE 802.11 network, an access point (i.e., a base station) communicates data with one or more remote receiving nodes over a wireless link. The wireless link may be susceptible to interference from other access points, other radio transmitting devices, or disturbances in the environment of the wireless link between the access point and the remote receiving node, among others. The interference may be to such a degree as to degrade the wireless link, for example, by forcing communication at a lower data rate. The interference also may be sufficiently strong enough to completely disrupt the wireless link.
One method for reducing interference in the wireless link between the access point and the remote receiving node is to provide several omnidirectional antennas for the access point, in a “diversity” scheme. For example, a common configuration for the access point comprises a data source coupled via a switching network to two or more physically separated omnidirectional antennas. The access point may select one of the omnidirectional antennas by which to maintain the wireless link. Because of the separation between the omnidirectional antennas, each antenna experiences a different signal environment, and each antenna contributes a different interference level to the wireless link. The switching network couples the data source to whichever of the omnidirectional antennas experiences the least interference in the wireless link.
Current methods that provide switching among antenna configurations, such as diversity antennas, and previous methods of controlling antenna segments, are unable to effectively minimize the interference from other access points, other radio transmitting devices, or disturbances in the environment of the wireless link between the access point and the remote receiving node. Typically, methods for antenna configuration selection are of the trial-and-error approach. In a trial-and-error approach, a transmission is made on each antenna configuration to determine which antenna configuration provides a more effective wireless link (e.g., as measured by a packet error ratio). The trial-and-error approach is inefficient, as it generally requires transmission on a “bad” antenna configuration to determine the poor quality of that antenna configuration. Further, the trial-and-error approach becomes increasingly inefficient with a large number of antenna configurations.
Additionally, current methods may require measurements of parameters such as voltage standing wave ratio, signal quality, or bit error rate for each antenna configuration. Such measurements can take a significant amount of time to compute, and may require large numbers of data packets to be transmitted before the measurements can be performed.